Melissopalynological characterization of the Lanzo Valleys honeys (Piedmont, northwestern Italy) as a reference for alpine productions and biodiversity conservation

Alpine areas are particularly famous for the honey produced as they can guarantee a non-contaminated environment and very diverse floral origin. Several studies have been published on honey produced in the Alps, and in particular on those from Piedmont (Ferrazzi and Marletto, 1980, 1985; Ferrazzi and Gerlero, 1996, 2001; Ferrazzi et al. 1999) and Valle d'Aosta (Ferrazzi, 1986, 2002; Adamo, 2003). There are also numerous studies on honey production in other Italian regions including Lombardy (Gianoncelli and Rossi, 2008), Venice (Ricciardelli d’Albore, 1995), Trentino Alto Adige (Vorwohl, 1972), Friuli Venezia Giulia (Gazziola, 2002), and Switzerland (Maurizio, 1958). The three Lanzo Valleys and four other neighboring valleys (Malone, Tesso, Ceronda, and Casternone) constitute an alpine area of the province of Turin (Piedmont, Northwestern Italy) characterized by continental climate with frequent rainfalls. They extend from 300 m above sea level to 3,380 m for Rocciamelone, and measure 781.56 km2. Migratory and sedentary beekeepers produce 10-50 kg of honey annually, depending on altitude, climate, and apiary management. In this study, the honeys of the Lanzo Valleys are analyzed in terms of floral origin using melissopalynological and sensorial analyses, the survey of the and compared with other Alpine honeys. The constant presence of the chestnut emerged, as this plant is widespread in the area, as well as by the presence of unifloral honeys. Chestnut pollen has been detected, albeit in small percentages, even in honeys produced at high altitude, and was observed as pollution of honeycombs in productions by migratory beekeepers and because bees can fly to lower parts of the valleys to forage on this species. Prunus (e.g. cherry) and Pyrus (Sorbus aria, S. aucuparia) pollen was present in almost all samples, sometimes reaching high percentages. A total of 72 pollen forms were found, which is less than most other alpine areas. Considering the floral origin of the honeys, the majority are multifloral, but unifloral honeys from Tilia spp., Rhododendron ferrugineum, Acer pseudoplatanus, and Robinia pseudoacacia (in the lower areas) were also found. The contribution of linden is important, which gives rise to bifloral honeys with Castanea sativa. The quantity of honeydew is poor. The Lanzo Valleys are located, from a melissopalynological aspect, in alpine zones "devoid of sainfoin", like other valleys in Piedmont (Sangone and Pellice Valleys), Valle d'Aosta (Champorcher and Lys Valleys), and in Trentino-Alto Adige (Vorwohl, 1972). The lower number of species useful to bees found in the surveys conducted in the Lanzo Valleys compared with other Alpine valleys is reflected in the lower diversity of pollens found in honeys. The widespread presence of the honey bee in the Lanzo Valleys and in other Alpine territories is essential for pollination, and therefore the for conservation of plant biodiversity in these areas, despite the steady decline of wild bees (Biesmeijer et al., 2012; Winfree et al., 2010).